Turbo - G Function Of Dfh System Design And The Realization Of Dsp

Because of the long transmission distance, low cost and invulnerability, short-wavecommunication occupies a very important position in military and emergencycommunications. Due to the existence of the various kinds of interference and multipathfading, it’s found that DFH radio communications almost interrupted in periods of poorchannel. And thus it is necessary to improve the existing DFH system to enhance itsall-weather ability to communicate in shortwave channel.Turbo-DFH technique introduces Turbo codes into DFH system, which caneffectively improve the error correction capability of the differential frequency hoppingsystem. Due to tail sequence do not participate in the iterative decoding and thus havepoor decoding performance in Turbo-DFH with random interleaver, this paperrepresents a new technique based on Self-Terminated Interleaver (STI), which calledSTI-Turbo-DFH, and simulates its performance comparison in different parameters(number of iterations, frame size, feed back coefficient) and different interferences,which include Partial Band Noise Jamming (PBNJ) and Multiple Tone Jamming (MTJ).The present Turbo-DFH decoding algorithm does not consider the overflow whichmay occur in the recursive factor calculation. This paper increased some treatment toprevent overflow and carried out a detailed derivation.Because the decoding algorithm of Turbo-DFH is complex, this paper representsseveral optimization methods and realizes the decoder of the Turbo-DFH in TI’s fixedpoint DSP Chip TMS320C6455successfully and tests its decoding performance.This article is divided into fiver chapters. Chapter1firstly introduces thecharacteristics of the shortwave communication and several spread spectrum techniques,and then describes the research status of DFH, and points out the main contents andstructure of this paper. Chapter2firstly introduces the Turbo codec structure andtraditional DFH system structure and working principle, and then gives the detailedderivation of the decoding algorithm which can prevent overflow on the basis ofdescribing the codec structure of Turbo-DFH, and then gives the simulation comparisonof two different kinds of DFH systems. The third chapter introduces two kinds of interleavers and its simulation performance comparison and then represents simulationperformance comparison in different parameters, which include the length of interleaver,coefficient, frequency number and the number of iterations and finally gives thesimulation analysis of anti-interference performance for STI-Turbo-DFH. Chapter4describes the specific details of the DSP implementation and represents severaloptimization methods for the simulation algorithm. The final chapter summarizes themain work in this paper and set out the next step of research.